The invention relates to novel ice confections containing an antifreeze protein. In particular the invention relates to novel ice confections in the form of thin, unsupported discrete pieces which are stable during packaging, storage and distribution.
It is highly desirable to be able to manufacture ice confections having novel shapes, properties and/or textures. Until now, however the ability to provide such a high degree of novelty and interest to the products has been limited. Products have to be manufactured with the ability to survive packaging, storage and distribution.
In particular, until now it has not been possible to provide thin, unsupported pieces of ice confection that are sufficiently strong enough to withstand packaging, storage and distribution regimes. Additionally, it has not been possible to provide such thin, unsupported pieces of ice confection which are also crispy, hard and brittle but still able to be bitten (i.e. they can fracture when eaten in the mouth). Obviously such thin, crispy, brittle products have a particularly high risk of breaking during packaging or transport
We have now shown that inclusion of specific antifreeze proteins into unaerated ice confections results in the formation of a strong, close-packed continuous network of ice crystals within the ice confection. As a result the ice confection is provided with specific defined mechanical properties. Such ice confections are able to be manufactured into thin, unsupported pieces which are brittle and crispy but nevertheless able to withstand packaging, storage and transportation.
WO 98/04146 (Unilever) discloses that AFPs can be incorporated into frozen food products such as ice confections to provide desirable product properties providing that the product and processing conditions are varied such that the ice crystals provided in the product have an aspect ratio of more than 1.9, preferably from 1.9 to 3.0. The specific examples given are all aerated ice cream compositions. As shown by comparative Examples A to C below, the addition of antifreeze proteins to aerated ice cream does not significantly change the mechanical properties of the ice cream. WO 98/04146 does not teach that it is possible to provide specific ice confection products having novel mechanical properties and that such ice confections can advantageously be used to provide thin, unsupported pieces.
WO 96/39878 (The Pillsbury Company) discloses a method for making a frozen composition for storage, the method not requiring a hardening step prior to storage. The frozen composition contains an antifreeze protein, in particular Type I AFP. Examples show the preparation of an aerated ice cream and an aerated frozen yogurt. As shown by comparative Examples A to C below, the addition of antifreeze proteins to aerated ice cream does not significantly change the mechanical properties of the ice cream. WO 96/39878 does not teach that it is possible to provide specific ice confection products having novel mechanical properties and that such ice confections can advantageously be used to provide thin, unsupported pieces.
U.S. Pat. No. 5,118,792 (Warren et al) discloses the addition of fusion proteins, and in particular the fusion protein protein A-Saf5 into foods which are to be consumed frozen, for example, ice cream, frozen yogurt, ice milk, sherbet, popsicles and frozen whipped cream. No examples are given where a final ice confection product is provided containing such fusion proteins. It is shown in Example 3B that when a popsicle formulation is used within the xe2x80x9csplat assayxe2x80x9d, growth of the ice crystals is restricted.
In our co-pending application PCT/EP98/08552 (published as WO 99/37164 on Jul. 29, 1999 after the priority date of the present application) a frozen food product comprising AFPs having an average ice crystal size of from 0.01 to 20 micrometers is disclosed. The application is concerned with reducing the aggregation of ice crystals as much as possible such that a soft, creamy product is provided. The examples disclose the manufacture of ice cream flakes. However, the ice cream used is aerated and as shown by Comparative Examples A to C below, such ice cream flakes are not self-supporting in that they collapse during storage and distribution. WO 99/37164 does not disclose that it is possible to provide thin, self-supporting, discrete pieces of ice confection which are stable to storage and distribution, providing that the ice confection has specific mechanical properties.
Accordingly the invention provides an unaerated ice confection in the form of thin, unsupported, discrete pieces which are stable during packaging, storage and distribution wherein the ice confection comprises an antifreeze protein and has the following mechanical properties;
xcex94 modulus/original modulusxe2x89xa70.4, and/or
xcex94 strength/original strengthxe2x89xa70.4; providing that when
xcex94 modulus/original modulusxe2x89xa66.0, xcex94 modulusxe2x89xa750 MPa, and/or
when xcex94 strength/original strengthxe2x89xa62.0,
xcex94 strengthxe2x89xa70.2 MPa.
By thin is meant 5 mm or less in thickness. Typically the thin layers will be from 0.5 to 5 mm in thickness. In particular approximately from 2 to 3 mm.
By pieces is meant for example flakes, sheets, tablets, slabs, shavings, chips, hoops, crisps or layers. In general the pieces will not be spherical. All dimensions are not identical. One dimension is from 0.5 to 5 mm and at least one other dimension is substantially longer than this.
By unsupported is meant that the thin crispy pieces are substantially in contact only with air and are not, for example, a layer upon a second ice confection which provides the thin layer with support.
Preferably xcex94 modulus/original modulusxe2x89xa70.4; providing that when xcex94 modulus/original modulusxe2x89xa66.0, xcex94 modulusxe2x89xa770 MPa, preferably xe2x89xa790 MPa, most preferably xe2x89xa7100 MPa.
Most preferably xcex94 modulus/original modulusxe2x89xa71.0; providing that when xcex94 modulus/original modulusxe2x89xa66.0, xcex94 modulusxe2x89xa7100 MPa, preferably xe2x89xa7200 MPa
Preferably xcex94 strength/original strengthxe2x89xa70.7. Most preferably xcex94 strength/original strengthxe2x89xa71.5.
By modulus is meant the apparent elastic modulus (E) as determined using a four point bend test. Example 1 gives the standard procedure for performing a four point bend test.
Therefore xcex94 modulus (xcex94E) means the change in modulus between two ice confections whose formulation and process of manufacture are identical in all respects except that the first ice confection includes in its composition an antifreeze protein, and the second ice confection has no antifreeze protein included in its composition (the control composition). Original modulus (Eorig) is the modulus measured in the control composition.
By strength is meant the flexure strength ("sgr"u) which can be defined as the maximum stress that a material can withstand, under the particular conditions. The flexure strength is given by the stress at a point of maximum force on the force versus displacement curve recorded during a four point bend test.
Therefore xcex94 strength (xcex94"sgr"u) means the change in strength between two ice confections whose formulation and process of manufacture are identical in all respects except that the first ice confection includes in its composition an antifreeze protein, and the second ice confection has no antifreeze protein included in its composition (the control composition). Original strength ("sgr"u orig) is the modulus measured in the control composition.
In addition to changes in the apparent elastic modulus and flexure strength, an increase in product hardness is provided by the ice confections according to the invention.
For ice confections frozen with agitation, for example in an ice cream freezer (such as a scraped surface heat exchanger), the increase in hardness can be measured using the Vickers hardness test. Details of the Vickers hardness test are given in Example 3.
The degree to which the Vickers Hardness (Hv) of the ice confection is increased by the addition of the antifreeze protein depends in part on the ice content of the ice confection.
However, generally xcex94Hv/Hv origxe2x89xa70.3, providing that when xcex94Hv/Hv origxe2x89xa65.0, xcex94Hvxe2x89xa70.3.
Preferably xcex94Hv/Hv origxe2x89xa71.0, providing that when xcex94Hv/Hv origxe2x89xa65.0, xcex94Hvxe2x89xa71.25.
Most preferably either xcex94Hv/Hv origxe2x89xa76.0 or xcex94Hv/Hv origxe2x89xa66.0 and xcex94Hvxe2x89xa72.0.
Where xcex94Hv is the change in Vickers Hardness between two ice confections whose formulation and process of manufacture are identical in all respects except that the first ice confection includes in its composition an antifreeze protein, and the second ice confection has no antifreeze protein included in its composition (the control composition). Hv orig is the original Vickers Hardness measured in the control composition.
By close-packed continuous network of ice crystals is meant that any given ice crystal is connected to at least one other ice crystal.
In unaerated ice confections which have been frozen with agitation, the degree of network formation can be measured as contiguity. Contiguity is defined as the ratio of the particle go particle interface area divided by the total interface area. It is thus a measure of the degree of network formation of the particle phase. Example 4 shows a method for the measurement of contiguity.
Unaerated ice confections according to the invention have a contiguity of at least 0.2 for an ice content of from 50 to 90%, preferably from 54 to 85% by weight, when measured at xe2x88x9218xc2x0 C.
In unaerated ice confections which have been frozen by any means, the degree of network formation can be measured as the Euler-Poincare characteristic of the ice phase. The Euler-Poincare characteristic is a measure of the degree of network formation of a particular phase. The lower and more negative the value of the Euler-Poincare characteristic, the greater the continuity of the phase in question. Example 5 shows a method for the measurement of the Euler-Poincare characteristic
Unaerated ice confections according to the invention have an ice phase Euler-Poincare characteristic of less than xe2x88x92150 mm as measured by the test given in Example 5 for an ice content of from 50 to 90%, preferably from 54 to 85% by weight, when measured at xe2x88x9218xc2x0 C.
By AFP is meant a protein which has significant ice recrystallisation inhibition properties as measured in accordance with Example 2. The AFP provides an ice particle size upon recrystallisation of less than 20 xcexcm, more preferred from 5 to 15 xcexcm.
Preferably the ice confection comprises at least 0.0005% by weight antifreeze protein, more preferably 0.0025% by weight antifreeze protein. Typically the ice confection will comprise from 0.0005% by weight to 0.005% by weight antifreeze protein.
For some applications it may be advantageous to include a mixture of two or more different AFPs into the food product.
The AFP for use in products of the invention can be any AFP suitable for use in food products. Examples of suitable sources of AFP are for example given in the article xe2x80x9cAntifreeze proteins and their potential use in frozen food productsxe2x80x9d, Marylin Griffith and K. Vanya Ewart, Biotechnology Advances, vol 13, pp375-402, 1995 and in patent applications WO 98/04699, WO 98/04146, WO 98/04147, WO 98/04148 and WO 98/22591.
The AFPs can be obtained from their sources by any suitable process, for example the isolation processes as described in the above mentioned documents.
One possible source of AFP materials is fish. Examples of fish AFP materials are antifreeze glycoproteins (AFGP) (for example obtainable from Atlantic cod, Greenland cod and Tomcod), Type I AFP (for example obtainable from Winter flounder, Yellowtail flounder, Shorthorn sculpin and Grubby sculpin), Type II AFP (for example obtainable from Sea raven, Smelt and Atlantic herring) and Type III AFP (for example obtainable from Ocean Pout, Atlantic wolffish, Radiated shanny, Rock gunnel and Laval""s eelpout). A preferred example of the latter type is described in WO 97/02343.
Another possible source of AFP material are invertebrates. Also AFPs may be obtained from Bacteria.
A third possible source of AFP material are plants. Examples of plants containing AFPs are garlic-mustard, blue wood aster, spring oat, winter cress, winter canola, Brussels sprout, carrot, Dutchman""s breeches, spurge, daylily, winter barley, Virginia waterleaf, narrow-leaved plantain, plantain, speargrass, Kentucky bluegrass, Eastern cottonwood, white oak, winter rye, bittersweet nightshade, potato, chickweed, dandelion, spring and winter wheat, triticale, periwinkle, violet and grass.
Both natural occurring species may be used or species which have been obtained through genetic modification. For example micro-organisms or plants may be genetically modified to express AFPs and the AFPs may then be used in accordance to the present invention.
Genetic manipulation techniques may be used to produce AFPs. Genetic manipulation techniques may be used to produce AFPs having at least 80%, more preferred more than 95%, most preferred 100% homology to the AFPs directly obtained from the natural sources. For the purpose of the invention these AFPs possessing this high level of homology are also embraced within the term xe2x80x9cAFPsxe2x80x9d.
The genetic manipulation techniques may be used as follows: An appropriate host cell or organism would be transformed by a gene construct that contains the desired polypeptide. The nucleotide sequence coding for the polypeptide can be inserted into a suitable expression vector encoding the necessary elements for transcription and translation and in such a manner that they will be expressed under appropriate conditions (for example in proper orientation and correct reading frame and with appropriate targeting and expression sequences). The methods required to construct these expression vectors are well known to those skilled in the art.
A number of expression systems may be utilised to express the polypeptide coding sequence. These include, but are not limited to, bacteria, yeast insect cell systems, plant cell culture systems and plants all transformed with the appropriate expression vectors.
A wide variety of plants and plant cell systems can be transformed with the nucleic acid constructs of the desired polypeptides. Preferred embodiments would include, but are not limited to, maize, tomato, tobacco, carrots, strawberries, rape seed and sugar beet.
For some natural sources the AFPs may consist of a mixture of two or more different AFPs.
Preferably the antifreeze protein is chosen such that it gives an aspect ratio of more than 1.9 to the ice crystal, preferably from 1.9 to 3.0, more preferably from 2.0 to 2.9, even more preferred from 2.1 and 2.8 (see WO 98/04146). Aspect ratio is defined as the maximum diameter of a particle divided by its minimum diameter. The aspect ratio can be determined by any suitable method. A preferred method is illustrated in the Examples (Example 6).
For the purpose of the invention the preferred AFPs are derived from fish. Especially preferred is the use of fish proteins of the type III, most preferred HPLC 12 as described in our case WO 97/02343.
Ice confections which are able to form thin, unsupported, discrete pieces and show the required change in mechanical properties on the addition of the antifreeze protein include unaerated milk containing frozen confections such as ice-cream, frozen yoghurt, and frozen custard, sherbet and milk ice, as well as unaerated frozen confections which do not typically contain milk such as water ices, sorbet, granitas and frozen fruit purees.
Preferably the ice confection is selected from an unaerated ice cream, water ice and milk ice.
By water ice is meant a frozen solution made essentially from sugar, water, fruit acid or other acidifying agent, colour, fruit or fruit flavouring.
By unaerated is meant an ice confection having an overrun of 10% or less (equivalent to 0.09 volume fraction of air). During the processing of the ice confection no deliberate steps such as whipping are undertaken to increase the gas content of the product. However, it should be realised that during normal methods for the preparation of non-aerated ice confections, low levels of gas or air may be incorporated into the product, for example due to the mixing conditions used.
Preferably the unaerated ice confection used to provide the thin, unsupported pieces will typically have an ice content of at least 30% by volume when measured at xe2x88x9218xc2x0 C., more preferably at least 40% by volume when measured at xe2x88x9218xc2x0 C., most preferably at least 50% by volume when measured at
The ice content may be determined following the techniques described in the article by B de Cindio and S Correra in the Journal of Food Engineering, Volume 24, pages 405-415, 1995 The enthalpy data required for this technique is obtained using adiabatic calorimetry (Holometrix Adiabatic Calorimeter). The ice contents as expressed herein are measured on an 80 g sample poured into the sample holder of the calorimeter and cooled to xe2x88x9275xc2x0 C. by placing the assembly in dry ice prior to placing in the calorimeter (precooled to between xe2x88x9270xc2x0 C. and xe2x88x9280xc2x0 C.). The enthalpy data obtained was analysed to give ice content as a function of the temperature following the method of Cindio and Carrera.
Preferably the unaerated ice confection used to provide the thin unsupported pieces has a total soluble solids content of less than 40% by weight, preferably less than 25% by weight, most preferably less than 15% by weight. For low calorie products, the total soluble solids content may be as low as, for example, approximately 5% by weight.
The total soluble solids content is measured at 4xc2x0 C. and is the % by weight of the total composition that is dissolved at that temperature.
The thin unsupported pieces of the invention have a reduced tendency to aggregate and therefore the free-flowing nature of the particulate material can be maintained over storage, even if the storage temperature is relatively high.
The invention is particularly useful for making frozen confectionery products akin to savoury snacks such as crisps, hoops, wafers, thin sticks etc. Typically each snack-like product will have a volume of from 0.5 to 40 ml, more preferred from 1 to 20 ml, especially 1.5 to 10 ml.
A further example of a product according to the invention is a flat lollipop.
The thin, unsupported pieces may be provided by any suitable process.
A first example process for the manufacture of thin, unsupported pieces includes quiescent freezing of a thin film of unaerated ice confection onto a slowly rotating drum freezer, and then scraping the frozen layer off. The frozen layer breaks up to provide thin pieces as discrete flakes.
A second example process for the manufacture of thin, unsupported pieces is by extrusion.